CN113790995B - Test device and method for measuring unsaturated soil-water characteristic curve - Google Patents
Test device and method for measuring unsaturated soil-water characteristic curve Download PDFInfo
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- CN113790995B CN113790995B CN202110855594.4A CN202110855594A CN113790995B CN 113790995 B CN113790995 B CN 113790995B CN 202110855594 A CN202110855594 A CN 202110855594A CN 113790995 B CN113790995 B CN 113790995B
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 76
- 238000000034 method Methods 0.000 title claims abstract description 37
- 238000012360 testing method Methods 0.000 title claims abstract description 31
- 239000002689 soil Substances 0.000 claims abstract description 80
- 238000007789 sealing Methods 0.000 claims abstract description 33
- 238000010438 heat treatment Methods 0.000 claims abstract description 21
- 238000005259 measurement Methods 0.000 claims abstract description 19
- 238000001704 evaporation Methods 0.000 claims abstract description 16
- 239000007921 spray Substances 0.000 claims abstract description 16
- 230000008020 evaporation Effects 0.000 claims abstract description 14
- 238000010521 absorption reaction Methods 0.000 claims abstract description 12
- 238000009423 ventilation Methods 0.000 claims description 27
- 239000011159 matrix material Substances 0.000 claims description 19
- 230000005540 biological transmission Effects 0.000 claims description 16
- 230000008569 process Effects 0.000 claims description 15
- 239000002274 desiccant Substances 0.000 claims description 14
- 238000003860 storage Methods 0.000 claims description 11
- 229910000831 Steel Inorganic materials 0.000 claims description 10
- 239000010959 steel Substances 0.000 claims description 10
- 238000007791 dehumidification Methods 0.000 claims description 9
- 239000000758 substrate Substances 0.000 claims description 8
- 230000009471 action Effects 0.000 claims description 6
- 239000011148 porous material Substances 0.000 claims description 6
- 239000010687 lubricating oil Substances 0.000 claims description 4
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- 239000011521 glass Substances 0.000 claims description 3
- 239000004033 plastic Substances 0.000 claims description 3
- 229920003023 plastic Polymers 0.000 claims description 3
- -1 polytetrafluoroethylene Polymers 0.000 claims description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 3
- 238000005303 weighing Methods 0.000 claims description 3
- 230000008859 change Effects 0.000 abstract description 5
- 238000013508 migration Methods 0.000 abstract description 3
- 230000005012 migration Effects 0.000 abstract description 3
- 238000012544 monitoring process Methods 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 4
- 238000011088 calibration curve Methods 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 239000012266 salt solution Substances 0.000 description 3
- 238000010998 test method Methods 0.000 description 3
- 238000009736 wetting Methods 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000013519 translation Methods 0.000 description 2
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- 238000007796 conventional method Methods 0.000 description 1
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- 238000009826 distribution Methods 0.000 description 1
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- 230000007613 environmental effect Effects 0.000 description 1
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- 239000003595 mist Substances 0.000 description 1
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- 239000003921 oil Substances 0.000 description 1
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
- G01N5/02—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by absorbing or adsorbing components of a material and determining change of weight of the adsorbent, e.g. determining moisture content
- G01N5/025—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by absorbing or adsorbing components of a material and determining change of weight of the adsorbent, e.g. determining moisture content for determining moisture content
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N5/00—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid
- G01N5/04—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by removing a component, e.g. by evaporation, and weighing the remainder
- G01N5/045—Analysing materials by weighing, e.g. weighing small particles separated from a gas or liquid by removing a component, e.g. by evaporation, and weighing the remainder for determining moisture content
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Abstract
The invention discloses a test device and a method for measuring an unsaturated soil-water characteristic curve, which are characterized in that: the system comprises a cylindrical box, a microwave heating system, a spray humidification system, an evaporation capacity testing system, a suction force measuring system, a balance measuring system and a rotation control system; sealing and heating the soil sample through a cylindrical box and a microwave heating system; realizing quantitative moisture absorption of soil body through a spray humidification system; the evaporation capacity is accurately controlled through an evaporation capacity testing system; monitoring the water content of the soil body and the change of the suction force in real time through a suction force measuring system and a balance measuring system respectively; and accelerating the moisture migration of the soil sample by a rotary control system. The device is simple and convenient to operate, fine in control, accurate in measurement and high in practicability, can provide new technical support for rapidly determining the unsaturated soil-water characteristic curve, and can be used for daily teaching work.
Description
Technical Field
The invention relates to the technical field of soil-water characteristic curve measurement, in particular to a test device and a test method for measuring an unsaturated soil-water characteristic curve.
Background
In a natural state, the soil body is subjected to multiple dry-wet circulation actions due to climate change such as rainfall infiltration and evaporation, so that the hydraulic-mechanical properties of unsaturated soil are obviously affected, the geotechnical engineering disaster caused by the dry-wet circulation actions is increasingly serious, and huge life and property losses are caused. In recent years, special attention has been paid to the effect of dry and wet cycle on the hydro-mechanical properties of unsaturated soils.
The soil-water characteristic curve (SWCC) is defined as the relationship of the suction force of the matrix with the weight water content (or saturation, volume water content), which is one of the most important constitutive relationships of unsaturated soil. The method reflects the water holding capacity of the soil body under the action of the matrix suction force, and can be used for predicting important parameters such as the osmotic coefficient, the deformation modulus, the strength and the like of the unsaturated soil, so that the method has very important significance in the unsaturated soil mechanics. The conventional methods for measuring the unsaturated soil-water characteristic curve by the current experiment comprise a simple evaporation method, a pressure plate method, a filter paper method, a salt solution method and the like, wherein the simple evaporation method only evaporates the water on the surface of the soil sample, so that the water content in the soil sample and the suction distribution of a matrix are extremely uneven, and the method only can obtain a dehumidification curve and has lower measurement reliability; the pressure plate method adopts an axial translation technology to translate the pore water pressure to zero, and directly controls the suction value of the matrix through the change of the pore air pressure, and has the defects in two aspects: on one hand, after each pressurization, the pressurization can be continued after the air pressure in the soil sample is stabilized, and the stabilization time is long at higher air pressure; on the other hand, the suction force in the axis translation environment and the natural environment is different, so that the measurement precision is low; the filter paper method needs to obtain a calibration curve of the filter paper, namely, a relation curve of the water content of the filter paper and the suction force of the matrix is established, then the water content of the soil sample and the suction force of the corresponding matrix are deduced according to the calibration curve, the method takes longer time, has high requirements on operators, and the accuracy, the temperature fluctuation and the balance precision error of the calibration curve directly influence the measurement result; the salt solution method controls the environmental humidity through different salt solutions so as to achieve the purpose of controlling the suction force of the soil sample matrix. In summary, the existing test technology has the disadvantages of time consumption, low automation level, inaccurate data acquisition, difficult judgment of suction balance conditions and the like.
Disclosure of Invention
In order to solve the problems, the invention discloses a test device and a test method for measuring an unsaturated soil-water characteristic curve, which are used for solving the problems of long measurement time and large measurement error of the unsaturated soil-water characteristic curve under the current dry-wet cycle.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
the test device for measuring the characteristic curve of the unsaturated soil and water comprises a cylindrical box, a microwave heating system, a spray humidification system, an evaporation capacity test system, a suction measuring system, a balance measuring system and a rotation control system, wherein the suction measuring system is installed in the cylindrical box, the balance measuring system is connected to the bottom of the suction measuring system, and the rotation control system is connected to the bottom of the balance measuring system; the interior of the cylindrical box is communicated with the spray humidification system, the evaporation capacity testing system and the microwave heating system.
Further improved, the cylindrical box is formed by splicing double-layer vacuum glass and a steel frame and is divided into an upper part and a lower part, and the upper part and the lower part are connected by adopting flange rings; the bottom of the cylindrical box is provided with an inner annular opening and an outer annular opening, and both sides of the inner annular opening and the outer annular opening are respectively provided with an inner sliding rail and an outer sliding rail; the center of the bottom of the cylindrical box is provided with a center hole, and a ball bearing is arranged at the center hole.
Further improvement, the inner piston sleeve and the outer piston sleeve are respectively embedded in the inner annular opening and the outer annular opening, an inner sealing sleeve and an outer sealing sleeve are respectively fixed on the inner piston sleeve and the outer piston sleeve, and the inner sealing sleeve and the outer sealing sleeve are respectively meshed with the inner sliding rail and the outer sliding rail.
Further improved, the rotation control system comprises a motor, the motor is connected with a transmission rod, the upper end of the transmission rod is connected with a rotating shaft, the rotating shaft is welded with a ball bearing at the bottom of the cylindrical box, and two ends of the welding part of the rotating shaft and the ball bearing at the bottom of the cylindrical box are sealed by T-shaped sealing rings; the transmission shaft is provided with a first rotary table and a second rotary table, the first rotary table is arranged outside the cylindrical box, and the second rotary table is arranged inside the cylindrical box.
Further improved, the balance measuring system comprises a balance base, the balance base and the first rotary table are fixed through bolts, a tray supporting rod is connected to the upper portion of the balance base, and the tray supporting rod penetrates through the annular opening and the second rotary table to enter the cylindrical box to be connected with a balance tray.
The suction force measuring system comprises a tensiometer base, wherein the lower end of the tensiometer base passes through a balance tray through a bolt to be fixed with a turntable II; the high-range tensiometer is fixed in the tensiometer base through an O-shaped sealing ring I; the tension meter is characterized in that two sides of the tension meter base are provided with a tail wing II, a thin-wall steel ring is fixed to the tail wing II through bolts, a tail wing I is fixed to the upper end of the thin-wall steel ring through bolts, and the tail wing I is a tail wing on a ring cutter.
Further improvement, the T-shaped sealing ring is made of polytetrafluoroethylene plastic; and lubricating oil is injected into the gap between the tray support rod and the annular opening to perform internal sealing.
The microwave heating system comprises an electromagnetic wave generator, an electromagnetic wave emitter, a transmission cable, a temperature control box and a thermometer, wherein the electromagnetic wave emitter is communicated with the inside of the cylindrical box and is electrically connected with the electromagnetic wave generator through the transmission cable; the measuring end of the thermometer is inserted into the cylindrical box, and the display end is arranged outside the cylindrical box; the spray humidification system comprises an ultrasonic generator, a water storage tank and a steam conduit, wherein the ultrasonic generator is fixed in the water storage tank, the water storage tank is communicated with the cylindrical tank through the steam conduit, and the steam conduit is provided with a steam valve and a flowmeter; the evaporation measurement system comprises a ventilation pipe, wherein the left end of the ventilation pipe is communicated with the bottom of the cylindrical box, and the right end of the ventilation pipe is communicated with the upper part of the cylindrical box; a second balance is arranged in the ventilation pipe, and a drying agent is placed on the second balance; the ventilating pipe is provided with a blower, and the left and right ends are respectively provided with a left valve and a right valve.
An experimental method of a test device for determining an unsaturated soil-water characteristic curve, comprising the following steps:
s1: installing a test device and checking air tightness;
s2: preparation of soil sample stageSegment: weighing a certain mass of soil sample according to a preset dry density, preparing a ring cutter sample, and recording the mass m of the dry soil sample d The method comprises the steps of carrying out a first treatment on the surface of the Opening the upper part of the cylindrical box, fixing the ring cutter on the base of the tensiometer, closing the upper part of the cylindrical box, and starting a dry-wet cycle test;
s3: soil sample moisture absorption stage: starting the spray humidification system for a period of time, wherein the flow meter water quantity is delta m 1w Opening a steam valve, introducing steam into the cylindrical box, and standing until the readings of the balance I and the high-range tensiometer are stable; opening the left valve of the ventilation pipe and the blower, synchronously opening the right valve of the ventilation pipe until the readings of the balance I, the balance II and the high-range tensiometer are not changed, and increasing the weight of the drying agent by delta m at the moment 2w Mass m of soil sample 1w And tensiometer reading (u) a -u w ) w Closing left and right valves of the blower and the ventilation pipe, and clearing balance readings; calculating the water content m of the soil sample at the moment 3w ＝(m 1w -m d +Δm 1w -Δm 2w ) And suction of the substrate (u) a -u w ) w ；u a Represents pore pressure, u w Represents pore water pressure, (u) a -u w ) w Represents the suction of the substrate during the moisture absorption process;
s4: repeating the step S3 for a plurality of times to obtain a soil-water characteristic curve of the moisture absorption process;
s5: soil sample dehumidifying stage: opening left and right valves of the ventilation pipe and the air blower, starting the microwave heating system to raise the temperature in the cylindrical box to 60-70 ℃, and synchronously starting the rotary control system until the readings of the balance I, the balance II and the high-range tensiometer are not changed, and increasing the weight of the drying agent by delta m at the moment 1d Mass m of soil sample 1d And tensiometer reading (u) a -u w ) d Closing the left and right valves of the microwave heating system, the rotary control system, the blower and the ventilation pipe, and clearing balance readings; calculating the water content m of the soil sample at the moment 3w ＝(m 1d -m d +Δm 1d ) And suction of the substrate (u) a -u w ) d ；(u a -u w ) d Represents the suction of the substrate during the dehumidification process;
s6: repeating the steps for a plurality of times to obtain a soil-water characteristic curve of the dehumidification process;
s7: combining the data obtained in the steps S3 and S5, drawing a moisture absorption-dehumidification overall process soil-water characteristic curve under the action of primary drying and wetting by taking the moisture content of the soil sample to be measured as an ordinate and the moisture content of the soil sample to be measured as an abscissa and taking the matrix suction force of the soil sample to be measured as an abscissa; and repeating the steps S3 and S6 until the target dry and wet cycle times are reached, and obtaining the unsaturated soil-water characteristic curve under multiple dry and wet cycles.
And (3) further improving, wherein the water content of the soil sample in the step (S3) and the step (S6) is determined by adopting a balance one and balance two-control average value taking method, and the soil sample matrix suction force is taken to obtain a stable value when the high-range tensiometer and the soil sample reach water potential balance.
The invention has the advantages that:
1. the spray humidifying system, the microwave heating system and the rotary control system are adopted to accelerate the uniform migration of moisture in the soil sample drying and wetting stage, so that the time required by the soil sample to reach suction balance is improved, and the time of the whole test is shortened to a great extent;
2. the balance measuring system and the suction measuring system are adopted to respectively measure the water content of the soil sample and the suction of the matrix, so that errors of manual recording of personnel and misjudgment of suction balance are reduced, and the automation level of the test is improved;
3. the balance measuring system and the evaporation measuring system are adopted to doubly monitor the change of the water content of the soil sample, and the average value of the water content is taken as the final water content of the soil sample; the change of the suction force of the soil sample matrix is monitored by adopting a suction force measuring system, and the matrix suction force stable value is taken as the final matrix suction force of the soil sample, so that the measuring precision and stability are remarkably improved.
Drawings
FIG. 1 is a schematic diagram of a test device for measuring an unsaturated soil-water characteristic curve;
FIG. 2 is a schematic diagram of a microwave heating system;
FIG. 3 is a schematic diagram of a suction force measurement system;
FIG. 4 is a schematic diagram of a balance measurement system;
FIG. 5 is a schematic view of the lower portion A-A of the cylindrical tank of FIG. 1;
FIG. 6 is a schematic view in section B-B of FIG. 5;
FIG. 7 is a schematic view of section C-C of FIG. 5.
In the figure:
1-1, a cylindrical box; 1-2, a flange ring; 1-3, a ball bearing; 1-4, stand columns; 1-5, a platform base; 1-6, an inner slide rail; 1-7, an outer slide rail; 2-1, an electromagnetic wave generator; 2-2, an electromagnetic wave emitter; 2-3, a transmission cable; 2-4, a temperature control box; 2-5, thermometer; 3-1, an ultrasonic generator; 3-2, a water storage tank; 3-3, a steam conduit; 3-4, a flowmeter; 3-5, a steam valve; 4-1, a ventilation pipe; 4-2, drying agent; 4-3, balance II; 4-4, an air blower; 5-1, a high range tensiometer; 5-2, soil sample; 5-3, cutting ring; 5-4, a tensiometer base; 5-5, O-shaped seal ring I; 5-6, a release agent; 5-7, a thin-wall steel ring; 5-8, a tail fin I; 5-9, a tail wing II; 6-1, balance one; 6-1a, a balance base; 6-1b, a tray supporting rod; 6-1c, balance tray; 6-2, inner sealing sleeve; 6-3, an outer sealing sleeve; 6-4, an inner piston sleeve; 6-5, an outer piston sleeve; 6-6, lubricating oil; 6-7, an O-shaped sealing ring II; 6-8, a ball ring; 7-1, a motor; 7-2, a transmission rod; 7-3, rotating shaft; 7-4, a first turntable; 7-5, a second turntable; 7-6, T-shaped sealing rings.
Detailed Description
The invention is further described below with reference to the drawings and examples.
Example 1
Referring to fig. 1 to 4, a test device for measuring an unsaturated soil-water characteristic curve comprises a cylindrical box 1-1, a microwave heating system, a spray humidification system, an evaporation capacity test system, a suction force measurement system, a balance measurement system and a rotation control system; the interior of the cylindrical box 1-1 is connected with a microwave heating system and a suction force measuring system; the outside of the cylindrical box 1-1 is connected with a spray humidification system and an evaporation quantity measurement system in a sealing way; the cylindrical box 1-1 is fixed on the upright post 1-4, and the upright post 1-4 is connected with the platform base 1-5; the balance measuring system passes through one end of the rotary disc II 7-5 and is connected with the suction measuring system, and the other end of the balance measuring system is fixed on the rotary disc I7-4; one end of the rotation control device is connected with the cylindrical box 1-1, and the other end of the rotation control device is fixed on the platform base 1-5.
Referring to fig. 1 and 5, the cylindrical box 1-1 is formed by splicing double-layer vacuum glass and a steel frame, and is divided into an upper part and a lower part, and the two parts are connected by adopting a flange ring 1-2; the bottom of the cylindrical box 1-1 is provided with an inner annular opening and an outer annular opening, and two sides of the opening are respectively provided with an inner sliding rail 1-6 and an outer sliding rail 1-7; the ball bearing 1-3 is arranged at the center opening of the bottom of the cylindrical box 1-1; the ball bearing 1-3 is welded with the rotating shaft 7-3, and a T-shaped sealing strip 7-6 is adopted to fill the gap at the end part.
Preferably, the inner surface of the cylindrical case 1-1 is coated with an electromagnetic wave reflecting material.
Referring to fig. 2, the microwave heating system is composed of at least an electromagnetic wave generator 2-1, an electromagnetic wave emitter 2-2, a transmission cable 2-3, a temperature control box 2-4, and a thermometer 2-5.
Referring to fig. 1, the spray humidification system comprises an ultrasonic generator 3-1, a water storage tank 3-2, a steam conduit 3-3, a flowmeter 3-4 and a steam valve 3-5; the ultrasonic generator 3-1 is fixed at the top of the water storage tank 3-2; a steam conduit 3-3 is arranged between the water storage tank 3-2 and the cylindrical tank 1-1 for connection; the steam conduit 3-3 is provided with a steam valve 3-5 and a flowmeter 3-4.
Referring to FIG. 1, the evaporation amount testing system at least comprises a ventilation pipe 4-1, a drying agent 4-2, a balance two 4-3 and a blower 4-4; the blower 4-4 can accelerate the moisture migration in the ventilation pipe 4-1 and the cylindrical box 1-1; the desiccant 4-2 may absorb moisture flowing therethrough; and the balance II 4-3 can weigh the weight of the drying agent 4-2.
As shown in FIG. 3, the suction force measuring system at least comprises a high-range tensiometer 5-1, a ring cutter 5-3, a tensiometer base 5-4, an O-shaped seal ring I5-5 and a thin-wall steel ring 5-7; the high-range tensiometer 5-1 is fixed on the tensiometer base 5-4 through an O-shaped sealing ring I5-5; the ring cutter 5-3 is provided with a tail 5-8, and the inner wall of the ring cutter is provided with a micro hole allowing moisture to pass through; the tensiometer base 5-4 is provided with a tail wing II 5-9; the first empennage 5-8 and the second empennage 5-9 are fixed on the thin-wall steel ring 5-7 by bolts.
Referring to fig. 4, 6-7, the balance measuring system at least comprises a balance one 6-1, an inner sealing sleeve 6-2, an outer sealing sleeve 6-3, an inner piston sleeve 6-4 and an outer piston sleeve 6-5; the balance I6-1 comprises a balance base 6-1a, a tray supporting rod 6-1b and a balance tray 6-1c; the inner sealing sleeve 6-2 and the outer sealing sleeve 6-3 are respectively connected with the annular inner sliding rail 1-6 and the annular outer sliding rail 1-7 in a meshed manner; the inner piston sleeve 6-4 and the outer piston sleeve 6-5 are respectively embedded into annular inner and outer openings at the bottom of the cylindrical box 1-1, and are externally sealed by adopting an O-shaped sealing ring II 6-7; the sealing sleeves are fixed on the corresponding piston sleeves, and drag-reducing ball rings 6-8 are arranged between the piston sleeves and the inner and outer sliding rails; the tray supporting rod 6-1b freely penetrates through the annular opening, and lubricating oil 6-6 is injected into the gap for internal sealing.
Referring to fig. 1, the rotation control system at least comprises a motor 7-1, a transmission rod 7-2, a rotating shaft 7-3, a first turntable 7-4 and a second turntable 7-5; one end of the motor 7-1 is fixed on the platform base 1-5, and the other end is connected with the transmission rod 7-2; the turntable I7-4 is connected with the platform base 1-5 by bolts; the second turntable 7-5 is connected with the tensiometer base 5-4 by bolts; the first turntable 7-4 and the second turntable 7-5 are coaxially connected with the rotating shaft 7-3 and the transmission rod 7-2 and are driven by the motor 7-1 to rotate.
Preferably, the first O-shaped sealing ring 5-5, the second O-shaped sealing ring 6-7 and the T-shaped sealing ring 7-6 are made of polytetrafluoroethylene plastics with good wear resistance, high temperature resistance and oil resistance.
Referring to fig. 1 to 7, a second object of the present disclosure is to provide a test method using the soil-water characteristic curve test apparatus as described above, comprising the steps of:
s1, installing a test device and checking whether the test device works normally or not; whether the valve connected with the cylindrical box is closed or not, whether the tightness is good or not, and starting a test after confirming that the tightness is correct or not;
s2, preparing soil samples: weighing a certain mass of soil sample according to a preset dry density, preparing a ring cutter sample by adopting a layered compaction method, and recording the mass m of the dry soil sample at the moment d The method comprises the steps of carrying out a first treatment on the surface of the Then the upper part of the cylindrical box is opened, a layer of isolating agent is coated on the base of the tensiometer, a cutting ring is fixed on the base of the tensiometer, the upper part of the cylindrical box is closed, and the following dry-wet cycle test is started;
s3, soil sample moisture absorption stage: adding a certain amount of water into the water storage tank; starting the spray humidification system for a period of time, and recording that the flow meter water quantity is delta m at the moment 1w Opening a steam valve, introducing steam into the cylindrical box, and standing for at least 2 hours until the first reading of the balance is not changed greatly, and the reading of the high-range tensiometer is stable, so that the soil sample can reach water vapor balance; opening a left valve of a ventilation pipe and an air blower, introducing uncondensed water vapor into the ventilation pipe, synchronously opening a right valve of the ventilation pipe to accelerate water vapor circulation until the weight of a drying agent on a balance I is no longer changed, reading of a soil sample on a balance II and a high-range tensiometer is no longer changed, and recording the weight increment delta m of the drying agent at the moment 2w Mass m of soil sample 1w And tensiometer reading (u) a -u w ) w Closing left and right valves of the blower and the ventilation pipe, and clearing balance readings; calculating the water content m of the soil sample at the moment 3w ＝(m 1w -m d +Δm 1w -Δm 2w ) And suction of the substrate (u) a -u w ) w The method comprises the steps of carrying out a first treatment on the surface of the Repeating the steps for a plurality of times to obtain a soil-water characteristic curve of the moisture absorption process;
s4, soil sample dehumidification stage: opening left and right valves of the ventilation pipe and the air blower, starting the microwave heating system to enable the temperature in the special model box to rise to 60-70 ℃, synchronously starting the rotary control device until the weight of the drying agent on the first balance is no longer changed, the weight of the soil sample on the second balance and the reading of the high-range tensiometer are no longer changed, and recording the weight increment delta m of the drying agent at the moment 1d Mass m of soil sample 1d And tensiometer reading (u) a -u w ) d Closing a microwave heating system, a rotary control device, left and right valves of a blower and a ventilation pipe, and clearing balance readings; calculating the water content m of the soil sample at the moment 3w ＝(m 1d -m d +Δm 1d ) And suction of the substrate (u) a -u w ) d The method comprises the steps of carrying out a first treatment on the surface of the Repeating the steps for a plurality of times to obtain a soil-water characteristic curve of the dehumidification process;
s5, combining the results of the step S3 and the step S4, drawing a soil water characteristic curve of the whole process of moisture absorption and moisture removal under the action of primary drying and wetting by taking the water content of the soil sample to be detected as an ordinate and the matrix suction force of the soil sample to be detected as an abscissa; and repeating the step S3 and the step S4 until the target dry and wet cycle times are reached, and obtaining the unsaturated soil-water characteristic curve under multiple dry and wet cycles.
And the water content of the soil sample in the step S3 and the step S4 is determined by adopting a balance one and balance two-control average value taking method, and the soil sample matrix suction force takes a stable value when the high-range tensiometer and the soil sample reach water potential balance.
In the step S3, water mist generated by the spray humidifying system is rapidly and uniformly diffused to the whole soil sample, so that the moisture absorption process of the soil sample is realized; in the step S4, the microwave heating system and the rotation control system adopt dual driving of temperature rising and centrifugal force to quickly transfer moisture, so that the dehumidification process of the soil sample is realized.
Although embodiments of the present invention have been disclosed above, it is not limited to the details and embodiments shown, which are well suited to various fields of use, and further modifications may be readily made by those skilled in the art without departing from the general concepts defined in the claims and the equivalents thereof, and therefore the invention is not limited to the specific details and illustrations herein.
Claims (1)
1. The test device for measuring the characteristic curve of the unsaturated soil, soil and water is characterized by comprising a cylindrical box, a microwave heating system, a spray humidification system, an evaporation capacity test system, a suction force measurement system, a balance measurement system and a rotation control system, wherein the suction force measurement system is installed in the cylindrical box, the balance measurement system is connected to the bottom of the suction force measurement system, and the rotation control system is connected to the bottom of the balance measurement system; the interior of the cylindrical box is communicated with the spray humidification system, the evaporation capacity test system and the microwave heating system; the cylindrical box is formed by splicing double-layer vacuum glass and a steel frame and is divided into an upper part and a lower part, and the upper part and the lower part are connected by adopting flange rings; the bottom of the cylindrical box is provided with an inner annular opening and an outer annular opening, and both sides of the inner annular opening and the outer annular opening are respectively provided with an inner sliding rail and an outer sliding rail; the center of the bottom of the cylindrical box is provided with a center hole, and a ball bearing is arranged at the center hole; an inner piston sleeve and an outer piston sleeve are respectively embedded in the inner annular opening and the outer annular opening, an inner sealing sleeve and an outer sealing sleeve are respectively fixed on the inner piston sleeve and the outer piston sleeve, and the inner sealing sleeve and the outer sealing sleeve are respectively meshed with the inner sliding rail and the outer sliding rail; the rotary control system comprises a motor, the motor is connected with a transmission rod, the upper end of the transmission rod is connected with a rotating shaft, the rotating shaft is welded with a ball bearing at the bottom of the cylindrical box, and two ends of a welded part of the rotating shaft and the ball bearing at the bottom of the cylindrical box are sealed by T-shaped sealing rings; the transmission rod is provided with a first rotary table and a second rotary table, the first rotary table is arranged outside the cylindrical box, and the second rotary table is arranged inside the cylindrical box; the balance measuring system comprises a balance base, wherein the balance base and a first turntable are fixed through bolts, a tray supporting rod is connected above the balance base, and the tray supporting rod penetrates through an annular opening and a second turntable to enter the cylindrical box to be connected with a balance tray; the suction force measuring system comprises a tensiometer base, and the lower end of the tensiometer base passes through a balance tray through bolts to be fixed with a turntable II; the high-range tensiometer is fixed in the tensiometer base through an O-shaped sealing ring I; the tension meter comprises a tension meter base, wherein two sides of the tension meter base are provided with a tail wing II, a thin-wall steel ring is fixed on the tail wing II through bolts, a tail wing I is fixed on the upper end of the thin-wall steel ring through bolts, and the tail wing I is a tail wing on a ring cutter; the T-shaped sealing ring is made of polytetrafluoroethylene plastic; the tray support rod and the annular opening are internally sealed by injecting lubricating oil into the gap; the microwave heating system comprises an electromagnetic wave generator, an electromagnetic wave emitter, a transmission cable, a temperature control box and a thermometer, wherein the electromagnetic wave emitter is communicated with the inside of the cylindrical box and is electrically connected with the electromagnetic wave generator through the transmission cable; the measuring end of the thermometer is inserted into the cylindrical box, and the display end is arranged outside the cylindrical box; the spray humidification system comprises an ultrasonic generator, a water storage tank and a steam conduit, wherein the ultrasonic generator is fixed in the water storage tank, the water storage tank is communicated with the cylindrical tank through the steam conduit, and the steam conduit is provided with a steam valve and a flowmeter; the evaporation amount testing system comprises a ventilation pipe, wherein the left end of the ventilation pipe is communicated with the bottom of the cylindrical box, and the right end of the ventilation pipe is communicated with the upper part of the cylindrical box; a second balance is arranged in the ventilation pipe, and a drying agent is placed on the second balance; the ventilating pipe is provided with a blower, and the left and right ends are respectively provided with a left valve and a right valve;
the experimental method for measuring the characteristic curve of the unsaturated soil, the soil and the water by adopting the experimental device comprises the following steps:
s1: installing a test device and checking air tightness;
s2: stage of preparing soil sample: weighing a certain mass of soil sample according to a preset dry density, preparing a ring cutter sample, and recording the mass m of the dry soil sample d The method comprises the steps of carrying out a first treatment on the surface of the Opening the upper part of the cylindrical box, fixing the ring cutter on the base of the tensiometer, closing the upper part of the cylindrical box, and starting a dry-wet cycle test;
s3: soil sample moisture absorption stage: starting the spray humidification system for a period of time, wherein the flow meter water quantity is delta m 1w Opening a steam valve, introducing steam into the cylindrical box, and standing until the readings of the balance I and the high-range tensiometer are stable; opening the left valve of the ventilation pipe and the blower, synchronously opening the right valve of the ventilation pipe until the readings of the balance I, the balance II and the high-range tensiometer are not changed, and increasing the weight of the drying agent by delta m at the moment 2w Mass m of soil sample 1w And tensiometer reading (u) a- u w ) w Closing left and right valves of the blower and the ventilation pipe, and clearing balance readings; the water content and the matrix suction force (u) of the soil sample at the moment are calculated a - u w ) w ；u a Represents pore pressure, u w Represents pore water pressure, (u) a- u w ) w Represents the suction of the substrate during the moisture absorption process;
s4: repeating the step S3 for a plurality of times to obtain a soil-water characteristic curve of the moisture absorption process;
s5: soil sample dehumidifying stage: opening left and right valves of the ventilation pipe and the air blower, starting the microwave heating system to raise the temperature in the cylindrical box to 60-70 ℃, and synchronously starting the rotary control system until the readings of the balance I, the balance II and the high-range tensiometer are not changed, and increasing the weight of the drying agent by delta m at the moment 1d Mass m of soil sample 1d And tensiometer reading (u) a- u w ) d Closing the microwave heating system, the rotary control system, the blower and the ventilation pipeThe right valve and the balance reading are cleared; the water content of the soil sample and the suction force of the matrix (u) at this time were calculated a- u w ) d ；(u a- u w ) d Represents the suction of the substrate during the dehumidification process;
s6: repeating the step S5 for a plurality of times to obtain a soil-water characteristic curve of the dehumidification process;
s7: and (3) drawing a soil water characteristic curve of the whole process of moisture absorption and moisture removal under the action of one time of dry and wet by combining the data obtained in the steps (S3) and (S5) and taking the moisture content of the soil sample as an ordinate and the matrix suction force of the soil sample as an abscissa; repeating the steps S3 and S5 until the target dry and wet cycle times are reached, and obtaining an unsaturated soil-water characteristic curve under multiple dry and wet cycles;
and the water content of the soil sample in the step S3 and the step S5 is determined by adopting a balance one and balance two-control average value taking method, and the soil sample matrix suction force takes a stable value when the high-range tensiometer and the soil sample reach water potential balance.
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